Improvised explosive devices (IEDs) are becoming the defacto standard for terrorist or paramilitary groups. The devices can be buried, concealed or disguised as everyday objects and left at transportation links or other populated or strategic places for surreptitious destruction. Chemical agents may be included within these devices to cause maximum threat potential. A suspect IED can halt all activity in the surrounding area for some time as the authorities determine the nature of the threat. Quite often, a remote explosive or biological detector has to be transported to the site to determine if the device is a positive threat. If the suspected IED is positioned in an awkward place, such as high up in a luggage rack of a train or in the luggage compartment of a bus, a remote detector may have difficulty accessing the suspected IED. In some cases, a human need to approach the device at an unsafe close distance to determine if the device is a positive threat. Vehicle convoys cannot stop and have every potential IED checked by either a remote detector or individuals. Such vehicles also need approximately 400 meters of detection distance when reaction times, safe standoff distances and speeds of 100 kph are all taken into account.
A recent special issue on sensors for the prevention of terrorist acts was published in the IEEE Sensors Journal, a publication of the IEEE Sensors Council, Volume 5, No. 4, August, 2005. Numerous methods for the detection of biological, explosive and chemical threats are described. However, known field portable units compromise detection performance to yield their small handheld size. Detection methods utilizing ion mobility spectroscopy (IMS), mass spectrometry (MS), gas chromatography (GC), Raman spectroscopy (RS), fiber-optic sensors and microwave spectroscopy all have the same problem with detecting substances at a distance in inaccessible positions.
Professor Loc Vu-Quo of the Mechanical and Aerospace faculty of the University of Florida has led a team of graduate students who have demonstrated the feasibility of using a consumer-off-the-shelf (COTS) paintball gun to fire a wireless Sticky Polymer Lethal Agent Tag (SPLAT) onto an intended target from a safe distance of approximately 20 meters away.
Biosensors as described by (W. D. Hunt et al “Time-dependent signatures of acoustic wave biosensors,” IEEE Proceedings, Vol. 91, no. 6, pp. 890-901, June 2003), (D. D. Stubbs, et al “Investigation of cocaine plumes using surface acoustic wave immunoassay sensors,” Analytical Chemistry, vol. 75, no. 22, pp. 6231-6235, Nov. 15, 2003), (Sang-Hun Lee et al “Real-Time Detection of Bacteria Spores Using a QCM Based Immunosensor,” Proceedings IEEE Sensor Symposium, 2003) and (Sang-Hun Lee et al “Vapor Phase Detection of Plastic Explosives Using a SAW Resonator Immunosensor Array” Proceedings IEEE Sensor Symposium, 2005) have been successfully assembled by immobilizing a monolayer of antibodies onto the surface of an acoustic wave (AW) device.